Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of financial services company Popular (Nasdaq: BPOP) have fallen 16% in intraday trading Monday on further economic worries.

So what: This is part of a massive bank sell-off today on continued worries that Greece will default. This seems to be a case of "same story, different day," but financials from Popular to Bank of America (NYSE: BAC) to Barclays (NYSE: BCS) are taking it on the chin today.

Now what: The Greek situation has been driving the market for more than a month, and after some positive developments last week we're back to panic mode. Shares of Popular have been falling for most of the year, and the banking decline in recent months has only hurt the stock. Popular did report a better-than-expected earnings report last quarter, so I would like to see how the third quarter was before jumping into these dangerous waters with both feet.

Interested in more info on Popular? Add it to your watchlist by clicking here.